Thornton said officials tried to negotiate with AGUA but were met with silence.

With rush-hour traffic humming behind him, Thornton said the long lines of idling cars are hurting the environment and causing a safety hazard. He accused AGUA of needlessly blocking a solution.

"This project is not going to make things worse. This project will make things better," Thornton said. "Automobiles will move. People will get to where they're trying to go. And many of those aquifer protection devices will be built into this project."

The authority plans to build ramps connecting U.S. 281 northbound to Loop 1604, and from Loop 1604 to U.S. 281 southbound. Ramps to relieve congestion off the loop to U.S. 281 heading north are not included in the project.

Over the years, residents have flocked to the North Side, and traffic at the site of the planned interchange often is clogged by gridlock. A planned toll road for U.S. 281 north of 1604 is on hold.

Meanwhile, construction of a "superstreet" concept with U-turns to increase traffic flow on U.S. 281 is under way.

The superstreet aims to reduce the length of stops at traffic signals by eliminating left turns onto the highway off feeder roads.

The highway intersection is located on the Edwards Aquifer recharge zone, where water seeps through porous limestone and replenishes the city's main drinking supply.

Insects known as "karst invertebrates" live in the sinkholes and caves of the recharge zone, and nine species in Bexar County have been declared endangered.

San Antonians have hotly debated the recharge zone and how to protect it for years. Environmentalists worry pollutants from roads, parking lots and other forms of "impervious cover" could seep into the aquifer.

AGUA posted a statement Wednesday on its website accusing transportation officials of "recklessly forging ahead" with a major highway project in an environmentally sensitive area.

"Instead of complying with laws intended to protect the people of San Antonio and their water supply, defendants are recklessly forging ahead using a "Categorical Exclusion" to avoid required environmental studies and safeguards," AGUA stated.

"In doing so, they are exploiting the same loophole in the law that BP used to hurry up and drill its 'Deepwater Horizon' well, and our federal agencies are standing by idly and rubber-stamping their plans."

County Judge Nelson Wolff said he was disappointed a compromise hadn't been reached.